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<br />36 <br /> <br />Streamban'~, <br /> <br />The streambank is the rising ground bordering a Istream channel below <br />the level of rooted terrestrial vegetation and above the normal streambed <br />(Figure 4). In entrenched channels the streambank and the valley wall may <br />coincide. By convention the left and right banks of lstreams are defined <br />looking downstream. In the absence of vegetation, me'ln annual high water <br />level defines the top of the strealllbank. Streambank height is the vertical <br />distance from the water level at any point in time (or from the lowest <br />point in the channel if the stream is dry) to the top of the lowest bank. <br /> <br /> <br />(LooHo. d"""",...) , ~ <br /> <br /> <br />W,n,d vid" --~~': <br /> <br />!~} <br />'__._~______: !lank he:lght <br />, , <br />; : Mu. depth <br />, , <br />: : <br />J : <br />, <br />, <br />~ <br /> <br />Channel. ....idth <br /> <br />Valley width <br /> <br />FIGURE 4 Str"eam CrOS$~5.!I:t iDn <br /> <br />Fro. T.W. Challlberl1n (ed). APD Technical Paper 2, Aquatic Sut'vey <br />Ter.inology. Briti8h ColUMbia Ministry of Environment. Victoria B.C. <br />]0 pagu. <br /> <br />Streambanks take on different forms and the range of bsnk fOl~ is <br />arbitrarily separated into four classes called ~, !epose, steel~, and <br />undercut, which reflect the status of the st.ream morphology (Figure 5) <br />(Chamberlin i980). A -flat- streambank is one where the bed SlOPE'S gently <br />to the beginning of rootedvegetation, frequently with overlappin~: bar <br />deposits. A reposed streambank is one that is eroded at high watE,r levels, <br />but is st the angle of repose of the unconsolidated material (usually 34. <br />to 370). Steep streambanks are nearly vertJ.cal, due to consolidation by <br />compaction, cementing or root structure of some other agent. An undercut <br />(cutbank) streambank is one that is undercut by erosional forces.- They <br />occur where a bank has been eroded by the stream to form a hollow <br />underwater. Usually the upper soil layers are so bound by root structures <br />that they remain intact. The effect is to e:reate a series of cavities <br />within the streambank which provide excellent cover (shelter) for fish and <br />wildlife. The depth of cutbanks is determined by probing with an aluminum <br />rod marked in meters. Average depth horizontally (int,o the bank) times the <br />length along the bank produces the area and when multiplied by the vertical <br />depth gives the volume. <br />